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#1 |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
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![]() Hi all! I've got a Vizio VO42L. Plug it in, and logo flashes orange/white for a bit, then solid orange. Press power, and logo changes to white. There is no backlight.
From reading some of the posts here I thought the inverter could have been the problem, but I've replaced it and still have the same issue. I noted that shining a flashlight on the screen shows nothing, so now I'm thinking main board? I took the following readings with the TV powered on. I also tried taking the readings with the CFL connectors unplugged - no change. Main board: Continuity across F1 & F2 = GOOD F1 = 5.12v F2 = 11.57v PSU Connector 1 (J21?): 24V = 24v SGND = 0v A = 0v B = 0v C = 0v PSU Connector 2 (J22?): PSON= 3.27v 12V = 11.57v SGND = 0v 5VSB = 5.16v A = 0v B = 0v C = 0v Inverter: Continuity across F1 = GOOD Left leg @ Q7 & Q9 = cycles between 0v-1.2v Middle leg @ Q7 & Q9 = 24.96v Right leg @ Q7 & Q9 = cycles between 0v-1.2v Top leg @ Q8 & Q10 = 0v Middle leg @ Q8 & Q10 = cycles between 0v-1.2v Bottom leg @ Q8 & Q10 = 0v Voltages @ connectors to CFLs = 0v Do you think I got a second bad inverter? Or do I have a bad main board? What should I try next? Thanks in advance for your help! --Dave Last edited by Daveleone; 02-20-2021 at 05:03 PM.. |
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#2 |
Badcaps Veteran
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
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Posts: 6,227
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![]() What voltages do you have on the Inverter Board connector
1, 2, 3, 4 & 5 = 6, 7, 8, 9 & 10 = 11 = 12 = 13 = 14 = Is the white fuse F1 showing continuity?
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#3 | |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
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![]() Quote:
1-5 = 24v 6-14 = 0v I double checked the voltages just to be sure the cable was good. F1 does have continuity. |
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#4 |
Badcaps Veteran
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
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![]() Can you provide a close up of what's given in the red box please.
The Inverter On signal appears to be missing. |
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#5 | |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
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![]() Quote:
12: VOnOff is 0V What should that voltage be? Should I jumper it to some other pin to see if the backlight will come on? Thanks! |
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#6 |
Badcaps Veteran
Join Date: Aug 2015
City & State: Cardiff
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![]() You need to check where the VonOff signal comes from. I would expect it to be around 3V when VonOff = On
Have you checked the two fuses shown in photo 6 of 11 in your first post. Last edited by dick_barton; 02-22-2021 at 01:02 PM.. |
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#7 | |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 153
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![]() That wire is connected to "B" on the PSU Connector 1 (J21?) (photo 3 of 11 in my first post)
Quote:
Continuity across F1 & F2 = GOOD F1 = 5.12v F2 = 11.57v |
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#8 | |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
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![]() Quote:
Anything else I should check on the main board? Or should I just order a replacement? |
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#9 |
Badcaps Veteran
Join Date: Feb 2010
City & State: S.F. Bay area
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Line Voltage: 120V 60Hz
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![]() I would start checking LDO Voltage Regulator IC's on the main board.
There is Main board repair kit and EEPROM also. https://www.shopjimmy.com/search.php...ery=Vizio+VO42
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Never stop learning Basic LCD TV and Monitor troubleshooting guides. http://www.badcaps.net/forum/showthr...956#post305956 Voltage Regulator (LDO) testing: http://www.badcaps.net/forum/showthr...999#post300999 Inverter testing using old CFL: http://www.badcaps.net/forum/showthr...er+testing+cfl Tear down pictures : Hit the ">" Show Albums and stories" on the left side http://s807.photobucket.com/user/budm/library/ TV Factory reset codes listing: http://www.badcaps.net/forum/showthread.php?t=24809 |
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#10 |
Senior Member
Join Date: Apr 2016
City & State: AZ
My Country: USA
Line Voltage: 120VAC 60Hz
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![]() Just to close this out, I was able to get a replacement main board for $20 from ElectroParts, so I decided to order it and save my time (instead of working on the defective board). The replacement main board worked.
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#11 |
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![]() Thanks for the feedback Dave.
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